Sentence Correction

Among lower- paid workers, union members are less likely than non union members to be enrolled in lower- end insurance plans imposing stricter limits on medical services and requiring doctors to see more patients, and spend less time with each.

a). imposing stricter limits on medical services and requiring doctors to see more patients, and spend
b). imposing stricter limits on medical services , requiring doctors to see more patients, and spending
c). that impose stricter limits on medical services, require doctors to see more patients, and spend
d). that impose stricter limits on medical services and require doctors to see more patients, and spending
e). that impose stricter limits on medical services, requiring doctors to see more patients and spending

In above sentence the OA is D.

I do not agree with the answer for the simple reason that whenever 'and' is preceded by a comma, what follows 'and' should be an element of list (provided list has more than two elements) or an independent clause. There is no other element to which 'spending' can co-relate.

Can someone help me understand??

Thanks